Democratic lawmakers are pushing for new legislation that would require greater disclosure of political ads that run on Internet platforms, despite a pledge by Facebook chief executive Mark Zuckerberg that the company will voluntarily pull back the curtain on political advertising on the social network.

Sens. Amy Klobuchar (Minn.) and Mark R. Warner (Va.) urged colleagues Thursday to support a bill that would create new transparency requirements for platforms that run political ads online akin to those already in place for TV stations, according to a letter obtained by The Washington Post.

The senators said that the Federal Election Commission, the independent agency that regulates political spending, “has failed to take sufficient action to address online political advertisements and our current laws do not adequately address online political advertisements published on platforms like Google, Facebook, and Twitter.”

While the senators suggested they were pleased that Zuckerberg promised to improve how Facebook reviews political ads and to enhance public visibility about who is purchasing them, they told colleagues, “This legislation would formalize, and expand, the transparency requirements Facebook has made.”

The bill would require digital platforms with more than 1 million users to create a public database of all “electioneering communications” purchased by a person or group who spends more than $10,000 on political ads online. In addition to storing a digital copy of the ad, the database would include a description of the targeted audience, the ad's view count, the date and time the ad ran, its price, and contract information for the purchaser.

The measure would create a reporting system similar to the one required of television stations by the Federal Communications Commission, which collects public information about political ads aired on TV and the names of the groups that sponsor them.

The proposed legislation – and the pledge by Facebook to create its own voluntarily disclosure system – puts new pressure on other tech companies such as Google and Twitter to determine whether they will adopt their own policies. Advocates for greater campaign finance disclosure have been stepping up their calls for greater oversight of online political ads, a long-dormant issue that the FEC may now reconsider.

When asked whether it will enact new policies regarding political ads, Twitter said it is open to discussing the issue with the FEC and Congress. Twitter added that it “deeply respects the integrity of the election process, a cornerstone of all democracies, and will continue to strengthen our platform against bots and other forms of manipulation that violate our Terms of Service.”

There are disclosure rules for online political spending. Under FEC rules, all political committees, individuals and groups that pay to run ads on an Internet platform must report their spending in public filings and include disclaimers on the ads themselves that state the ads' sponsors — just as they do for television ads.

However, as social media has played a growing role in campaigns, the commission has not drawn clear lines on what is required of small, character-limited political ads online. As recently as 2011, Facebook argued to the FEC that such ads should not require the usual disclaimer that runs with political messages because it would be inconvenient and impractical.

The revelations that Russian-financed ads ran on Facebook during the 2016 campaign prompted the usually divided FEC last week to reopen a long-delayed assessment of whether it should require more robust disclosure in online ads. The panel voted unanimously to seek public comments on whether it should update its Internet rules — drafted back in 2006 -- when it comes to small, online messages. Ellen Weintraub, the Democratic commissioner who is calling for the new rulemaking, has said she plans to invite representatives from tech companies such as Facebook, Twitter and Google to attend a public hearing to discuss potential new regulations.